The overall goal of this project remains to understand how a cell coordinates the expression of its genetic repertoire during normal growth and during nutritional deficiency. We have focused on E. coli and the regulatory effects of guanosine 3 feet,5 feet bis-pyrophosphate, (ppGpp) particularly at the level of ribosomal RNA (rRNA) transcription. Cellular rRNA transcription is regulated as a function of growth rate and ppGpp concentration; this event directly and indirectly accounts for most of cellular mass and energy consumption. For at least moderate growth rates, rRNA accumulates stably in ribosomes roughly in proportion to the square of the growth rate such that rRNA:DNA ratios are an inverse, linear function of ppGpp basal levels. At very slow growth rates and during energy source deprivation two exceptions to this relation occur. First rRNA is transcribed in excess over amounts assembled into ribosomes and second, rRNA transcription occurs despite elevated ppGpp levels. Work this past year has led to an explanation of these exceptions as well as finding unusual anti-termination features of rRNA operon transcription. 1. The upstream (P1) promoter behaves as if it is regulated by ppGpp and is exponentially activated by growth rate and dominates transcription during fast growth. 2. The downstream (P2) promoter is a constitutive maintenance promoter, only weakly activated by growth rate, which dominates transcription during slow growth and during energy source deprivation. 3. A region between the P2 promoter and the first structural gene (16S RNA) in the rrn operon encodes an antitermination function enabling transcripts arising from either P1 or P2 to read through ordinarily efficient terminators. This region shows DNA sequence homology to the well known Lambda N dependent system, but occurs in the absence of lambda. One host protein used by lambda (NusA) has been implicated. 4. The ribosomal terminators are super efficient, capable of stopping both ribosomal transcripts as well as N anti-terminated lambda promoted transcripts.